POY Spinning Machine

Overview

A POY spinning machine turns solid polyester chip into continuous filament yarn that is partially oriented but not fully drawn. It belongs to the melt-spinning family: the polymer is melted, pumped, forced through fine holes, cooled into solid filaments, and wound onto packages. What separates POY from fully drawn yarn is the take-up speed. Winding at roughly 3000-3600 m/min stretches the soft filaments enough to give them moderate molecular orientation and dimensional stability, while leaving them with residual draw capacity. That residual draw is used later in draw-texturing, where POY is drawn and crimped into textured yarn for apparel and home textiles.

The machine is built around a Spin Beam & Metering carrying several spinning positions in a row. Each position has its own Metering Pump, Spin Pack, quench column, godet set and Winder. The shared services, chip drying, the Extruder, beam heating, quench air conditioning and the control system, feed every position from one supply so the yarn comes out identical end to end.

Chip drying and feed

PET is hygroscopic, and water in the melt causes hydrolysis that breaks the polymer chains and drops the intrinsic viscosity. So the chip is dried hard before it ever reaches the screw. The Crystalliser first raises the chip crystallinity so it will not soften and clump, then the Drying Hopper gives it several hours of dwell in hot dry air. The Desiccant Dryer keeps that air at a dew point near -40 C by cycling twin molecular-sieve beds. Dried chip is conveyed to the extruder feed and metered in through a Rotary Feed Valve that also seals the dry-air loop.

Melt preparation

The Extruder is a single-screw machine. Its Extruder Screw has feed, compression and metering sections that take the chip from solid to a homogeneous melt as the Barrel Heater Band bands hold each zone between 285 and 300 C. The screw also acts as the pump that pushes melt forward against the back pressure of the spin packs. A Melt Filter removes gels and contaminants, and Melt Pressure Sensor transducers watch the pressure to protect the machine and flag a clogging pack.

From the extruder the melt enters the Spin Beam & Metering. The beam is a heated box that holds every position at exactly the same temperature using condensing diphenyl vapour from the Vapour Heating System. Inside the beam, one Metering Pump per position delivers a fixed volume of melt per revolution. Because denier is set by melt volume divided by take-up speed, this gear pump is what makes the yarn count repeatable, and the Metering Pump Drive turns all the pumps together so positions match.

Spinning and quench

Each Spin Pack filters the melt a final time through a bed of graded steel sand, then forces it through the Spinneret. The number of holes sets the filament count and the hole diameter sets the as-spun fineness. The molten strands emerge downward into the Quench Chimney, where a low-turbulence cross-flow of conditioned air from the Quench Air Conditioning cools them below the glass transition and solidifies them. A Spin Tube just under the spinneret delays the start of cooling so the filaments attenuate evenly. Cooling rate and air uniformity strongly affect filament quality, so the quench air temperature and humidity are held tight. As the bundle converges it passes a Finish Applicator that meters spin finish onto it for filament cohesion, lubrication and static control, fed by a Finish Metering Pump.

Take-up and orientation

The solidified yarn is drawn down by the Godet & Take-Up Draw. The driven Godet Roll sets the surface speed, and that speed, near 3200 m/min for standard POY, is what partially orients the polymer. Each godet runs on its own Godet Drive for steady speed, and a Separator Roll spaces the yarn wraps so they do not overlap. An Interlace Jet then entangles the filaments at intervals so the bundle stays together through winding and the next process.

The Winder lays the yarn onto tubes. The Traverse Unit reciprocates the yarn across the tube to build an even package while the Contact Roll sets winding speed and package density. A Tension Sensor feeds the Winder Drive, which ramps spindle speed down as the package grows so surface speed and tension stay constant. When a package is full the Spindle Turret swings a fresh tube into place so the line never stops.

Controls and utilities

The Control & Drives ties the line together. A PLC sequences heating, melt delivery, quench and take-up, while the Operator HMI shows temperatures, speeds and tensions across the positions. A cabinet of Servo Drive units, each built on its own Servo Motor, runs the metering pumps, godets and winders to their set points. The whole machine sits on a multi-level Frame & Enclosure with the spin beam at the top and the winders below, with guarding and a Service Walkway for access to the spin packs and threadlines.

Use

POY is rarely a final product. It is the standard feedstock for draw-texturing, where it is drawn to its final orientation and false-twist textured into bulky yarn for knit and woven fabrics. A POY line is therefore judged on uniformity: tight control of melt temperature, quench, finish pick-up and take-up speed across every position keeps denier, dye uptake and downstream texturing behaviour consistent across thousands of packages.